Submersible vehicle buoyancy control

ABSTRACT

A fail-safe electro-hydraulic control system varies the buoyancy of a submersible vehicle to facilitate variation of the vehicle&#39;&#39;s operating depth by independent propulsion apparatus. A closedloop hydraulic circuit determines the proper degree of water ballast storage, simultaneously storing energy in a pressure tank for direct rapid fail-safe restoration of buoyancy to the vehicle in the vent of a system failure.

United States Patent May 30, 1972 Gustafson [541 SUBMERSIBLE VEHICLEBUOYANCY CONTROL [72] Inventor: Roy H. J. A. Gustaison, Sea Clifi, NY.

[73] Assignee: Sperry Rand Corporation [22] Filed: Sept. 18, 1970 [21]Appl. No.: 73,276

[52] U.S.Cl ..l14/16E 511 ..B63g 8/00 [58] Field of Search ..1 14/16 E,16 R, 235 B, 0.5 R; 9/8 R; 61/69 R [56] References Cited UNITED STATESPATENTS 863,532 8/1907 Hector ..1 14/16 E 2,972,972 2/1961 Allen..ll4/l6E 3,204,596 9/1965 Fallon ..ll4/l6E Primary Examiner-Trygve M.Blix Attorney-S. C. Yeaton ABSTRACT A fail-safe electro-hydrauliccontrol system varies the buoyancy of a submersible vehicle tofacilitate variation of the vehicles operating depth by independentpropulsion apparatus. A closed-loop hydraulic circuit determines theproper degree of water ballast storage, simultaneously storing energy ina pressure tank for direct rapid fail-safe restoration of buoyancy tothe vehicle in the vent of a system failure.

11 Claims, 1 Drawing Figure 35c INCREASE 2 DECREASE FROM PRESSURE SUPPLYPatented May 30, 1972 201 4 DECREASE 24 :7 FROM 205 PRESSURE SUPPLY 209104 1100 L i To SUMP INVENTOR R0) HL/A. GUSTAFSO/V A TTOR/VEYSUBMERSIBLE VEHICLE BUOYANCY CONTROL BACKGROUND OF THE INVENTION 1.Field of the Invention The invention relates generally to submersiblevessels of the type including a capability for generally verticaldescent or ascent in a body of water. The invention more particularlypertains to buoyancy control systems for such vessels for facilitatingpropulsion of the vessel to a selectable predetermined water depth andfor its maintenance substantially at that depth.

2. Description of the Prior Art In the recent past, there has beenintensive development of several types of oceanographic vessels forperforming various work functions in the undersea environment, such assurveying, mineral and biological sampling, rescue, and kindredfunctions. Such undersea vehicles have included manned and unmannedsubmersibles of the self-propelled, towed, and otherwise remotelycontrolled types.

.Such vehicles have generally lacked stable and versatile means forbuoyancy control. Since'efficient and safe control of buoyancy insubstantially vertical descent or ascent is desired, techniquesavailable for the control of more conventional military submarines arefound to be inadequate, those techniques requiring a significant degreeof longitudinal motion of the vessel. These and other techniquesavailable suffer because of complexity and large size, weight, and costof apparatus and often require the use of special, untried components.Such deficiencies feature attendant high costs of installation,maintenance, and repair.

Available buoyancy control techniques do not offer a capacity for rapidbut accurately controlled change from one state of buoyancy to anotherand accordingly do not lend themselves to fully satisfactory fail-safeoperation and to quick corrective response under conditions of partialor total failure of the control system or of its energy supply.Corrective response to a failure generally makes heavy demands upon theprimary power supply of the vehicle which, under the circumstances of aserious failure, may already be faced with large demands upon itscapacity as, for instance, by the vessel propulsion system.

SUMMARY OF THE INVENTION The invention is a fail-safe and efficientelectrically-controlled hydraulic system for the determination of thebuoyancy of a submersible vehicle in holding, ascent, descent, oremergency modes. Control of buoyancy is achieved by the intake orexpulsion of ballast water from the vehicle by means of hydraulic forcesapplied against the external sea water through a flexible but imperviouswall of an actuator in the form of a transfer barrier tank. The transferbarrier pressure tank stores sea water to a degree determined by aclosed-loop hydraulic system operated by a constant speed, non-reversingpump. Energy is simultaneously stored in a pressure tank during normaloperation of the closed-loop hydraulic system. Such energy isautomatically available in the event of electrical or hydraulic failurefor the purpose of expelling sea water from the barrier transfer tankand thereby for safely restoring the buoyancy of the vehicle.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE is a diagrammaticrepresentation of the novel hydraulic system, partly in cross section,and of its as sociated electrical control circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention utilizes a closedhydraulic control system, using both air or other gasses and a suitableoil or other liquid as hydraulic fluid media, in cooperation with anelectrical control system for the automatic adjustment of the buoyancyof an underwater vehicle or vessel. Control of buoyancy is achieved bythe intake or expulsion of water ballast such as sea water from thevehicle by means not requiring longitudinal motion of the vehiclethrough the water.

A principal element of the control system, as seen in the sole figure,is a pressure vessel 1 which serves as an energy storage element,normally containing hydraulic liquid and a gas such as air or nitrogenunder considerable pressure. Pressure vessel 1 will be spoken ofhereinafter as the air-oil pressure tank 1 in view of the character ofthe fluids found most convenient for use therein, though it is to beunderstood that fluids other than air and oil may be used. Tank 1 may beconstructed of metal, although spherical fiber glass tanks are found tobe inexpensive, light in weight, and otherwise to be suitable, sincethey are known to withstand pressure as great as 5,000 pounds per squareinch absolute (p.s.i.a.) in 12.5 inch diameter sizes, for example.

Energy stored in air-oil pressure tank 1 is supplied and augmented foruse within the closed hydraulic system by a hydraulic liquid pump 17 ina manner yet; to be described. Pump 17 may be any of severalconventional available types, such as the fixed volume, positivedisplacement, multiple piston, liquid pumps of the type manufactured byVickers Division, Sperry Rand Corporation, Detroit, Mich., includingVickers type number MF-l0-39l l-25. The latter device has a rated outputof substantially eight gallons per minute at 3,750 revolutions perminute.

Automatic control hydraulic liquid flow is performed in part, by aseries 8, 12, l3, l4, l5 and 24 of conventional balanced poppet vales.Such leakage proof valves are readily available on the market andinclude means for solenoid control of the position of a spring-retumedpoppet valve armature so as to prevent or to permit fluid flow throughthe poppet valve. Valves 12, 13, 14, and 15, as will be seen, open inpairs according to the setting of selector switch 35.

A further principal element of the system is the transfer barrier tank 6which performs as the controlled actuator for the system, itrepresenting the actuator element which takes in or expels ballast waterin the process of changing the buoyancy of the vehicle. The transferbarrier tank actuator 6 also serves to isolate the closed hydraulicliquid control system from the ballast water, preventing the corrosiveaction of, for example, sea water within the closed hydraulic system. Asis seen in the figure, actuator 6 has a pressure-tight casing 48 withapertures 25 and 26 at its respective ends. Apertures 25 and 26 are notin direct mutual communication because the flexible ovate bladder 7 issealed in leak-proof manner adjacent opening 25 so that only thatopening communicates with the interior 47 of the bladder 7. The interior47 of bladder 7 is filled with'a hydraulic fluid such as oil and itssize expands or contracts according to the pressure of hydraulic liquidat input 25. The remaining volume 27 of case 48 is filled with ballastwater. It is clear that other types of actuators may be employed, suchas an actuator comprising a simple piston moving in a cylinder anddriven by hydraulic fluid, one face of the piston being in directcontact with the sea water.

As previously noted, the invention is versatile in nature, beingadaptable to use in a variety of kinds of submersible vehicles orvessels, towed or self-propelled, manned or unmanned. In suchapplications, the apparatus appearing below line AA in the figure willnormally be aboard the vehicle, in some cases mounted largely on itsexterior surfaces. A manned vehicle may have the apparatus above lineA-A within its closed interior. On the other hand, an unmanned vehiclewould generally have the apparatus above line A-A located near the oceanor lake surface, as on a ship such as a tender for the submarine.Electrical cables of sufficient length to permit the vehicle to submergeto a desired depth would connect the parts above and below line A-A inthe latter instance.

The novel buoyancy control system may be applied in a submersiblevehicle, for example, of the general type disclosed in the Gerald R.Keatinge patent application Ser. No. 9,759 for a Remotely ControlledUnmanned Submersible Vehicle", filed Feb. 2, 1970 and also assigned tothe Sperry Rand Corporation. Application Ser. No. 9,759 discloses aremotely controlled submersible vehicle having a rigid truss frameworksuspended from a floatation sphere, three horizontally disposed membersof the truss framework being arranged to form a triangular assemblyabout a vertically oriented center post affixed to the sphere.Hydraulically actuated propellors are mounted at each comer of thetriangular assembly to provide motion control in as many as six degreesof freedom, depending on the relative magnitude and direction of thethrust generated by the respective propellors. In operation, power issupplied to the vehicle and commands transmitted thereto for propellingit and directing it to perform various assigned tasks through a tethercable connected from the vehicle to a manned surface or subsurfacevessel or other control station.

In any event, all of the hydraulic apparatus, including the abovementioned elements 1, 6, 8, 12, 13, 14, l5, l7, and 24, lies below lineA-A of the figure and is found aboard the submersible vehicle. Assumingthat the vehicle is provided with a central supply of hydraulic liquidunder pressure, that supply or any other convenient supply may be usedto drive pump 17 through the agency of a conventional hydraulic motor18, which may also be of the multiple piston type, driving pump 17through shafting 22 and flexible coupling 21. The central pressuresource (not shown) is coupled to motor 18 through throttle valve 23depending upon the open or closed state of solenoid 34 actuated balancedpoppet valve 24. Solenoid 34 is operated by electrical power suppliedvia lead 210 from the active contacts associated with relay blades 32and 33. Throttle valve 23 provides a convenient means for adjusting thespeed of motor 18 to a desired substantially constant value. Valve 23may be adjusted according to the speed of response desired of thehydraulic control system. It will be understood that pump 17 and motor18 may be provided in the conventional manner with case drains so thatsea water is excluded from their interiors.

Hydraulic pump 17 is adapted to supply hydraulic liquid from sumpmanifold 100 to a high pressure manifold 101. When the hydraulic controlsystem is not demanding sufficient flow of hydraulic liquid, pump 17 maybe relieved of working against excessively high back pressure by aconventional relief valve 19 (set, for example, to open at 2,000p.s.i.g.) located in pipe 102 connecting manifolds 100 and 101 andpermitting flow from manifold 101 to manifold 100. Under certain otherconditions of operation of the hydraulic system, a tendency to forcefluid flow in the opposite sense may prevail. To remove the undesiredeffect of such an oppositely directed pressure, an appropriatelyoriented conventional check valve 20 is placed in pipe 103 permittingflow from manifold 100 to manifold 101. High pressure manifold 101 mayalso be equipped with a conventional filter 16.

Pressure manifold 101 is connected through filter 16 to a port of thebalanced poppet valve 12, whose second port is connected to pipe 104.The output of filter 16 is similarly connected to a port of the balancedpoppet valve 13, whose second port is connected to pipe 105. It is to beunderstood that hydraulic liquid under pressure in manifold 101 whichpasses the opened poppet valve 12 may flow through pipe 104,

to the interior 47 of bladder 7 of the transfer barrier tank 6.Likewise, hydraulic liquid under pressure in manifold 101 mayalternatively flow through the opened poppet valve 13 and pipe 105 tothe interior of air-oil pressure tank 1, thus increasing the pressure ofthe gas therein and storing energy.

Sump manifold 100 is connected to a port of balanced pop pet valve 14,whose second port is connected to pipe 104. The sump manifold 100 issimilarly connected to a port of the balanced poppet valve 15, whosesecond port is connected to pipe 105. It is to be understood thathydraulic liquid may flow through poppet valve 12 or 14 relative to thetransfer barrier tank 6 or relative to the air-oil pressure tank 1 whenpoppet valves 13 and 15 are opened.

Pipes 104 and 105 are joined through pipes 106 and 107 adjacent theair-oil pressure tank 1 and the transfer barrier tank 6 through certainseries connected hydraulic elements. The

latter series elements include the normally closed balanced poppet valve8, a conventional relief valve 9 set, for example,

to open at p.s.i.a.) and a conventional check valve 10.

The closed hydraulic system may be opened for filling first with ahydraulic liquid and then with the appropriate quantity of air or othergas to a desired pressure level by use of manual valve 4 in pipe 108branching from pipe 105. Excess gas may be bled from the hydraulicsystem by opening the closed hydraulic system with valve 11, found inpipe 109 branching from pipe 107.

Certain pressure sensors aid in controlling the operation of thehydraulic system by measuring pressure and by opening and closingelectrical contacts. These sensors include pressure sensor 2 whichoperates electrical switch 39, pressure sensor 3 which operateselectrical switch 38, and pressure sensor 5 which operates electricalswitch 43. Sensors 2, 3, and 5 are respectively individually connectedby pipes 110, 111, and 1 12 so that they measure pressure proximate theair-oil tank 1.

The electrical control circuit cooperates with switches 38, 39, and 43and is supplied with electrical current from source 29 through themanual on-off switch 30. Closure of switch 30 supplies electrical powervia lead 200 to the relay switch blades 32 and 33 and to the arm 35 of afirst manual selector switch, and via lead 201 to solenoid 36 of poppetvalve 8, holding it in its closed position. The blade of selector switch35 may be manually placed on one of three contacts 35a, 35b, or 350. Todecrease buoyancy, contact 35a is selected and, to increase buoyancy,contact 35c is used. When no change is desired, contact 35b may be used.Contact 35a is coupled by lead 202 to the switch blade 43 associatedwith pressure sensor or pick off 5. Contact 35c is connected to the arm37 of a second manual selector switch which has contacts 37a and 37b.Contact 37a is selected if the vehicle is to be operated in an upperregion bounded by the sea surface, as for instance, at depths betweenzero and 500 feet. On the other hand, contact 37b may be chosen foroperation at lower water depths say, from 500 to 2,000 feet. Contact 37ais connected via lead 203 to the switch blade 38 associated withpressure pick off 3. Likewise, contact 37b is connected via lead 204 tothe switch blade 39 associated with pressure pick off 2.

Switch 39 has contacts 39a and 39b, contact 39a being connected to pilotlight 31. Contact 39b is coupled by lead 205 to leads 206 and 207 andthence respectively to solenoids 41 and 42, respectively associated withbalanced poppet valves 12 and 15. Switch 38 has contacts 38a and 38b,contact 380 also being connected to pilot light 31. Contact 38b iscoupled via lead 205 to leads 206 and 207 and therefore alsorespectively to solenoids 41 and 42. In addition, contact 38b isconnected by lead 205 through lead 211 to the solenoid 40 controllingrelay blade 33. Switch 43 has contacts 43a and 43b, contacts 43a beingcoupled via leads 208 to solenoid 44 associated with relay switch 32. Inaddition, contact 43a is connected by lead 209 to solenoids 45 and 46,respectively associated with balanced poppet valves 12 and 13. Thesecond contact 43b of switch 43 is connected to pilot or monitor lamp28.

Operation of the system is initiated manually by closing the powerswitch 30. When the vessel is to be submerged, mode selector switch 35is then placed on contact 35a, commanding a decrease in buoyancy of thevessel by operating solenoid 44 and poppet valves 13, 14, and 24.Electrical power is thereby supplied via relay switch blade 32 and lead210 to solenoid 34, opening poppet valve 24. High pressure hydraulicliquid is thus connected from the vessels main hydraulic pressure supplyaccording to the setting of throttle valve 23 to drive the hydraulicmotor 18. In turn, hydraulic pump 17 is driven at a substantiallyconstant speed and is ready to supply hydraulic liquid under pressure asdirected by balanced poppet valves 12, 13, 14, and 15 so as to controlthe effective buoyancy of the undersea vessel.

With poppet valves 13 and 14 open, pump 17 transfers hydraulic liquidfrom the interior 47 of the transfer barrier tank 6 through pipe 104,poppet valve 14, manifold 100, manifold 101, poppet valve 13, and pipeto the interior of the air-oil pressure tank 1. As hydraulic liquid isremoved from the interior 47 of transfer barrier tank 6, ballast waterenters the interior 27 of tank 6 via aperture 26 and the buoyancy of thevessel progressively decreases. This program stores energy withinair-oil pressure tank 1 which energy is readily available for recoveryat all times should a quick increase in the buoyancy of the vessel orsurfacing be demanded. Pump 17 will continue to operate in this way,relief valve 19 performing in the usual-manner, until the setting ofmode selector switch 35 is manually changed or until the operatingpressure of pressure pick off 5 is reached (for instance, 2,0l5p.s.i.a.) in the air-oil pressure tank 1. Should the latter eventobtain, switch blade 43 is automatically moved to the contact 43b.Monitor lamp 28 is illuminated while relay armature 44 moves switchblade 32 so that poppet valve 24 is closed and hydraulic motor 18 isstopped. The energy stored in air-oil pressure tank is none-the-lessinstantly available should a command to increase buoyancy be executed bymoving selector switch 35 to contact 35c.

It will be understood that the interior 47 of bladder 7 is initiallyfilled with a hydraulic liquid or oil, minimizing the volume 27available for intrusion of ballast or sea water. Displacing thehydraulic liquid or oil from interior 47 increases the volume 27 ofballast water to a value determined by the size of barrier tank 6 andthe amount of hydraulic liquid or oil pumped from tank 6. Air-oilpressure tank 1 is a pressure vessel normally initially filled with airto atmospheric pressure or, otherwise, to an alternative pressuredetermined by the maximum desired operating depth of the submersiblevessel. For example, the respective volumes of tanks 1 and 6 may bechosen to allow ballast or sea water intake sufficient to change thebuoyancy of the vessel by 30 pounds and to give a pressure within theair-oil pressure tank 6 after transfer of hydraulic fluid from thetransfer barrier tank of 2,015 p.s.i.a, In one application, such apressure is sufficiently in excess of the sea water pressure on thevessel at a depth of 2,000 feet to insure return of the vessel to apositive buoyancy state, for example, upon failure of the electrical orhydraulic power supply systems.

Should it be desired to increase the buoyancy of the vessel in thenormal manner, mode selector switch 35 is placed on contact 350 so thatelectrical power may be fed through switch blade 37 and lead 203 toswitch blade 38 and through contact 38b and lead 205 and thencerespectively via leads 206 and 207 to solenoids 41 and 42, opening therespective balanced poppet valves 12 and 15. Application of electricalpower to lead 205 and thus to lead 211 permits solenoid 40 to move relayswitch blade 33 to supply power, as before, to hold poppet valve 24open, permitting motor 18 to drive pump 17, as before.

With balanced poppet valves 12 and open, hydraulic liquid is pumped fromthe air-oil pressure tank 1 through pipe 105, poppet valve 15, manifolds100 and 101, poppet valve 12, and pipe 104 to the interior 47 of bladder7 of the transfer barrier tank 6. As the interior 47 of bladder 7 fillswith hydraulic liquid, ballast or sea water is expelled through aperture26 and the vessels buoyancy increases, permitting the vessel to beraised even more rapidly toward the surface by propulsion means whichmay be operated independently of the present invention. Operation ofpump 17 continues until the setting of mode selector switch 35 ischanged or until the commanded pressure level is achieved in the air-oilpressure tank 1 as detected by pressure pick off 3. The actuation pointof switch 38 operated by pick off 3 may be set, for example, at 15p.s.i.a. Consequent movement of switch blade 38 to contact 38a permitsbalanced poppet valves 12, 15, and 24 to close shutting down operationof the system. Motion of blade 38 to the contact 38a causes monitor lamp31 to be illuminated, indicating to the observer that the initialcondition of vehicle buoyancy has been restored.

In the foregoing discussion of the operation of the apparatus forincreasing the buoyancy of the vessel, it was assumed that the depthselector switch 37 was manually placed on contact 37a. This setting ofswitch 37, it will be understood, determines operation of the system inthe region between the ocean surface and a submerged depth, forinstance, of 5,000 feet. Similar apparatus operating in an analogousmanner may be employed for controlling the vessel at greater depths suchas, for instance, between 500 and 2,000 feet.

Should it be desired to increase the buoyancy of the vessel when it isoperated at a depth below 500 feet, the mode selector switch 35 is againplaced on contact 350, while switch blade 37 is moved to contact 37b. Inthis manner, electrical power may be fed through switch blade 37 andelectrical lead 205. The electrical power then travels, as before, vialeads 211, 206, and 207 to solenoids 41 and 42, causing the opening ofrespective poppet valves 12 and 15. Application of electrical power tolead 205 and thus also to electrical lead 211 again permits the solenoid40 to operate, moving relay switch blade 33 to supply power, as before,via electrical lead 210 to hold poppet valve 24 open, permitting motor18 to continue to drive hydraulic pump 17. With balanced poppet valves12 and 15 open, hydraulic liquid is again pumped from the air-oilpressure tank 1 through pipe 105, poppet valve 15, manifold 100,manifold 101, poppet valve 12, and pipe 104 to the interior 47 ofbladder 7 of the transfer barrier tank 6. Again, as the interior 47fills with hydraulic liquid, ballast water is expelled through aperture28 of tank 6. Consequently the vessels buoyancy increases, placing thevessel in condition to be raised rapidly toward the ocean surface byconventional means ordinarily employed to move the vessel along agenerally vertical path.

Operation of hydraulic pump 17 continues until the setting of modeselector switch 35 is changed or until the pressure level commanded bythe setting of depth selector switch 37 is achieved in the air-oilpressure tank 1 as detected by pressure pick off 2. The actuation pointof switch 39 operated by pick off 2 may be set, for example, at USp.s.i.a. Consequent movement of switch blade 39 to contact 390 againpermits balanced poppet valves 12, 15, and 24 to close, shutting downoperation of the hydraulic system. In addition, motion of blade 39 tocontact 39a again causes the pilot lamp 31 to be illuminated or othermonitoring means to be activated. lllumina' tion of lamp 31 indicates tothe observer that the desired initial condition of vehicle buoyancy hasbeen restored. It is seen that the presence of the two pressure pickoffs 2 and 3 and their associated circuits permits restoration of thesystem to one of two selectable initial pressure conditions during theincrease-buoyancy cycle.

As has been seen, the novel buoyancy control system has significantfeatures permitting flexibility of operation under variouscircumstances, including the storage of energy in airoil pressure tank 1which is used to facilitate changes in buoyancy of the vessel. Of equalimport is the adaptability of the same control system to affordfail-safe operation of the vessel under failure conditions. For example,a failure in the electrical system automatically closes any of balancedpoppet valves 12, 13, 14, or 15 which may be open and passing hydraulicfluid, but automatically opens the normally closed poppet valve 8,solenoid 36 failing to hold the valve armature 8a in its closed positionagainst a spring which is a conventional internal part of valve 8.

Should electrical failure occur when the vessel is in a positive stateof buoyancy, the above described state of balanced poppet valves 8, 12,13, 14, and 15 prevents any further intake of ballast or sea water intothe interior 27 of barrier tank 6.

Should electrical failure occur when the vessel is in its neutral stateof buoyancy, automatic conversion to positive buoyancy is assured. Inthe neutral state, the pressure within airoil tank 1 exceeds thesurrounding sea water pressure. Electrical failure, permitting balancedpoppet valve 8 to open, rapidly dumps that stored pressure through pipes106 and 107 into the interior 47 of barrier tank 6. Consequently, arapid discharge of ballast water from the interior 27 of tank 6 comesabout, abruptly increasing the buoyancy of the vessel.

Should a failure appear in the hydraulic system that prevents operationof pump 17, the buoyancy control switch blade 35 is simply placed on itsinactive contact 35b. This event restores positive buoyancy of thevessel also by opening solenoid 36 controlled poppet valve 8, all otherbalanced poppet valves returning to the closed position. Again,hydraulic fluid is transferred from the air-oil pressure tank 1 to theinterior 47 of barrier tank 6 and ballast or sea water is rapidlydischarged from interior 27. Relief valve 9 is included between lines106 and 107 to permit retaining a 110 p.s.i.a. minimum initial pressurein the barrier tank 6 during the discharge cycle. Thus, the system maybe automatically recycled upon reaching the surface without rechargingpressure tank 1 with air.

Fail-safe operation is fulfilled even at maximum depths for the vehicle,being insured by the automatic operation of the buoyancy control system,in the event of either electrical or hydraulic failure. That automaticoperation is ensured because the buoyancy control system fills air-oilpressure tank 1 to a pressure determined by the pressure setting ofswitch during the decrease buoyancy mode of operation. The quantity ofballast or sea water discharge by the buoyancy control system when afailure is experienced depends upon the pressure level available inair-oil pressure tank 1, the ambient sea water pressure, and the amountof ballast or sea water within the interior 27 of tank 6. Increasedoperating depth diminishes the quantity of ballast water discharged but,as the vessel rises toward the ocean surface, additional ballast wateris discharged from tank 6. Finally, as the air-oil tank 6 reaches theselected initial ambient pressure condition, the maximum vessel buoyancyis restored.

It will be appreciated by those skilled in the art that various changesfalling clearly within the true scope of the invention may be made. Forexample, it has been convenient to speak of sea water and of the oceanin describing operation of the invention, while it is apparent that thebuoyancy control system may be successfully operated in other bodies ofliquid. Only one operating depth range may be employed, or several maybe added by the addition of pressure pick offs such as sensors 2 and 3and their associated circuits. Representative operating characteristics,such as representative pressure levels, have been cited with regard tothe system and its components, but it is to be understood that suchvalues are merely representative, and that other values may necessarilybe chosen depending upon the nature of the submersible vehicle to becontrolled.

While the invention has been described in its preferred embodiment, itis to be understood that the words that have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from thetrue scopeand spirit of the invention in its broader aspects.

1 claim:

1. Apparatus for controlling a submersible vessel comprismg:

hydraulically actuatable means for transfer of ballast liquid forchanging the buoyancy of said vessel,

energy storage means containing a compressible gas,

hydraulic pump means, hydraulic valve means for permitting reversiblehydraulic liquid flow between said hydraulically actuatable means andsaid energy storage means through said pump means,

means operating said hydraulic valve means for commanding a change ofbuoyancy of said vessel, and

means responsive to the pressure level within said storage means foroperating said hydraulic valve means to prevent hydraulic liquid flowtherethrough when said commanded change is substantially completed.

2. Apparatus as described in claim 1 wherein said means for transfer ofballast liquid comprises:

substantially rigid tank means having first and second port means,

expansible barrier bladder means within said tank means and having portmeans sealed in leak-proof communication with said first port means ofsaid tank means,

said tank means and said barrier bladder means being so constructed andarranged as to permit transfer of ballast liquid through said secondport means in substantial proportion to transfer of hydraulic fluidthrough said first port means without co-mingling of said liquids.

3. Apparatus as described in claim 1 wherein said energy storage meanscomprises pressure tank means adapted to store hydraulic fluid and acompressible gas under pressure.

4. Apparatus as described in claim 1 wherein said hydraulic pump meanscomprises:

unidirection hydraulic pump means having input and output port means,and

substantially constant velocity motor means for driving saidunidirectional pump means.

5. Apparatus as described in claim 4 wherein said hydraulic valve meanscomprises:

first and second valve means each having first and second port means,said first port means being connected to said hydraulic pump output portmeans, and

third and fourth valve means each having third and fourth port means,said third port means being connected to said hydraulic pump input portmeans.

6. Apparatus as described in claim 5 wherein:

said second port means of said first valve means and said fourth portmeans of said third valve means are connected to said means for transferof ballast liquid, and

said second port means of said second valve means and said fourth portmeans of said fourth valve means are connected to said energy storagemeans.

7. Apparatus as described in claim 6 wherein said means operating saidhydraulic valve means for commanding a change of buoyancy of said vesselcomprises:

electrical power source means,

means for supplying electrical power to said motor means,

manual switch means connected to said electrical power source means forselecting the polarity of said buoyancy change,

first circuit means connected to said switch means for actuating saidfirst and fourth valve means for permitting liquid flow therethrough,and

second circuit means connected to said switch means for actuating saidsecond and third valve means for permitting liquid flow therethrough.

8. Apparatus as described in claim 7 wherein said means responsive tothe pressure level within said storage means comprises:

first pressure sensor means connected to said storage means, and

first switch means activated by said first pressure sensor means,

said first switch means being connected in said first circuit fordeactivating said first circuit at a first predetermined pressure level.

9. Apparatus as described in claim 7 wherein said means responsive tothe pressure level within said storage means comprises:

second pressure sensor means connected to said storage means, and

second switch means activated by said second pressure sensor means,

said second switch means being connected in said second circuit fordeactivating said second circuit at a second predetermined pressurelevel.

10. Fail-safe means for use in apparatus of the type described in claim1 for automatically providing an increase in buoyancy of said vessel inthe event of power failure, comprismg:

hydraulic circuit means for by-passing said hydraulic valve means andsaid hydraulic pump means and directly connected to said energy storagemeans and to said ballast liquid transfer means,

hydraulic valve means included in said hydraulic circuit means, and

means for opening said hydraulic valve means in the event of said powerfailure for automatically causing rapid discharge of ballast liquid fromsaid ballast transfer means.

11. Apparatus as described in claim 10 wherein means is ineluded in saidhydraulic circuit means for preventing complete discharge of saidstorage means.

1. Apparatus for controlling a submersible vessel comprising: hydraulically actuatable means for transfer of ballast liquid for changing the buoyancy of said vessel, energy storage means containing a compressible gas, hydraulic pump means, hydraulic valve means for permitting reversible hydraulic liquid flow between said hydraulically actuatable means and said energy storage means through said pump means, means operating said hydraulic valve means for commanding a change of buoyancy of said vessel, and means responsive to the pressure level within said storage means for operating said hydraulic valve means to prevent hydraulic liquid flow therethrough when said commanded change is substantially completed.
 2. Apparatus as described in claim 1 wherein said means for transfer of ballast liquid comprises: substantially rigid tank means having first and second port means, expansible barrier bladder means within said tank means and having port means sealed in leak-proof communication with said first port means of said tank means, said tank means and said barrier bladder means being so constructed and arranged as to permit transfer of ballast liquid through said second port means in substantial proportion to transfer of hydraulic fluid through said first port means without co-mingling of said liquids.
 3. Apparatus as described in claim 1 wherein said energy storage means comprises pressure tank means adapted to store hydraulic fluid and a compressible gas under pressure.
 4. Apparatus as described in claim 1 wherein said hydraulic pump means comprises: unidirection hydraulic pump means having input and output port means, and substantially constant velocity motor means for driving said unidirectional pump means.
 5. Apparatus as described in claim 4 wherein said hydraulic valve means comprises: first and second valve means each having first and second port means, said first port means being connected to said hydraulic pump output port means, and third and fourth valve means each having third and fourth port means, said third port means being connected to said hydraulic pump input port means.
 6. Apparatus as described in claim 5 wherein: said second port means of said first valve means and said fourth port means of said third valve mEans are connected to said means for transfer of ballast liquid, and said second port means of said second valve means and said fourth port means of said fourth valve means are connected to said energy storage means.
 7. Apparatus as described in claim 6 wherein said means operating said hydraulic valve means for commanding a change of buoyancy of said vessel comprises: electrical power source means, means for supplying electrical power to said motor means, manual switch means connected to said electrical power source means for selecting the polarity of said buoyancy change, first circuit means connected to said switch means for actuating said first and fourth valve means for permitting liquid flow therethrough, and second circuit means connected to said switch means for actuating said second and third valve means for permitting liquid flow therethrough.
 8. Apparatus as described in claim 7 wherein said means responsive to the pressure level within said storage means comprises: first pressure sensor means connected to said storage means, and first switch means activated by said first pressure sensor means, said first switch means being connected in said first circuit for deactivating said first circuit at a first predetermined pressure level.
 9. Apparatus as described in claim 7 wherein said means responsive to the pressure level within said storage means comprises: second pressure sensor means connected to said storage means, and second switch means activated by said second pressure sensor means, said second switch means being connected in said second circuit for deactivating said second circuit at a second predetermined pressure level.
 10. Fail-safe means for use in apparatus of the type described in claim 1 for automatically providing an increase in buoyancy of said vessel in the event of power failure, comprising: hydraulic circuit means for by-passing said hydraulic valve means and said hydraulic pump means and directly connected to said energy storage means and to said ballast liquid transfer means, hydraulic valve means included in said hydraulic circuit means, and means for opening said hydraulic valve means in the event of said power failure for automatically causing rapid discharge of ballast liquid from said ballast transfer means.
 11. Apparatus as described in claim 10 wherein means is included in said hydraulic circuit means for preventing complete discharge of said storage means. 